On the battlefield, the armed forces rely heavily on collapsible fabric storage containers for temporary storage of fuel and water. These bulk containers range in size from 3000 gallons to 210,000 gallons, and because they are made of fabric such containers assume different size and shape depending on the amount of liquid in their interior. Bulk fabric tanks of this type pose several technical difficulties in accounting for the volume of fuel and water used by the armed forces, due to problems in accurately measuring volume in a container of variable size and shape.
The current method for tracking the volume of fuel or water in bulk fabric storage containers is to measure the liquid as the container is filled or emptied using flow meters. One limitation of flow meters is that they are relatively inaccurate. It has been found that volume measurements taken on the contents of existing bulk fabric storage containers by flow meters may vary as much as 6% to 10%, plus or minus, compared to actual volume. This assumes that the flow meters are reset on a daily basis. If the flow meters are not reset, the accuracy is even worse due to cumulative error.
Another issue with bulk fabric storage containers is that even if current measurement techniques were capable of accurately determining volume levels during filling and/or emptying, the walls of such containers are semi-permeable and liquid can be lost through the walls via diffusion. Losses also occur through the venting system of the container. Consequently, volume measurements depending on flow meters are subject to further inaccuracies as liquid is pumped in or out of the container during use.